Abstract: An improved bicycle ergometer system is disclosed which reduces the limitation on the work input necessary to operate the device and, at the same time, accomplishes an increase in the relative amount of isotonic exercise provided by operation of the system. The system provides real-time auxiliary energy input control based on the instantaneous difference between the actual operator work rate and the intended work rate. The preferred embodiment includes a stationary bicycle frame having a pedal and crank assembly mechanically coupled to an output shaft. A clutch-connected, double-ended electric motor can be used to provide the rotational torque necessary to bring the output shaft up to a desired speed, if desired, prior to the onset of a physical output test. It can also control the intended work rate to a level of zero operator work rate input. In one embodiment, a flywheel is also mounted on the motor output shaft.